Download Introduction

Learing outcomes


Introduction to Unix system
Unix commands
What is a UNIX?


UNIX is an operating system
An operating system is the program
that controls all the other parts of a
computer system, both the hardware
and software.
What is LINUX



LINUX is a free UNIX-type operating
system originally created by Linus
Torlvads with the assistance of
developers around the world.
The source code for Linux is freely
available to everyone.
The commands of linux are similar to
unix.
Features of UNIX

UNIX is a multi-user, multi-tasking
operating system.



Multi-users may have multiple tasks
running sumiltaneously.
This is different than PC operating system
UNIX is a machine independent
operating system.

Designed from the beginning to be
independent of the computer hardware
Introduction unix


Developed at Bell Laboratories in the
late 1960s by Dennis Ritchie and Ken
Thompson
Shell is simply a program that reads in
the commands you type and converts
them into a form that is more readily
understandable by the UNIX system
Introduction (continue.)



Shell includes some fundamental
programming constructs that let you
make decisions, loop, and store values
in variables
“Bourne” shell was written by Stephen
Bourne in Bell laboratories
“Bourne” shell is the “standard” shell
UNIX System

The “UNIX system” is logically divided
into two pieces:


Kernel
Utilities
UNIX System (continue.)

Kernel is the heart of the UNIX system and resides in the
computer’s memory. It allocates time and memory to programs
and handle filestore and comunications
UNIX
system
kernel
Utilities
disks
Memory
UNIX System (continue.)



Utility resides on the computer’s disk
and are only brought into memory as
requested.
Virtually every command under UNIX is
a utility
Shell is a utility program loaded into
memory for execution whenever you
log into the system
Logging in a UNIX system

Terminal is connected to a UNIX system
through




Direct wire
Modem
LAN
After you connect the UNIX system a
login: message appears
Logging in a UNIX system (continue.)
login:
getty
UNIX
SYSTEM
KERNEL
login:
getty
getty
login:
Logging in a UNIX system (continue.)




init is the UNIX system
init automatically starts up a getty program
on each terminal port whenever the system is
allowing users to log in
After getty displays the message login: and
some types the usernames followed by
RETURN, it starts up a program called login
to finish the process of logging in. Then getty
disappears
/etc/passwd file has one line per user
Logging in a UNIX system (continue.)
login: Skan
password:
login
login:
UNIX
SYSTEM
KERNEL
getty
getty
login:
Logging in a UNIX system (continue.)



After login begins execution, Password:
message appears
User types the password and hits
RETURN
The user name and the password will
be checked against the corresponding
entry in the file /etc/passwd
Logging in a UNIX system (continue.)


Every line has seven fields separated by “:”.
The fields are :
1.
2.
3.
4.
5.
6.
7.
Login name
Password (encrypted form).
User ID
Group ID
User information which could be First and Last name,
etc…
Home directory
Program to start up when user logs in. Usually a “shell”
program
Logging in a UNIX system (continue.)

Example
$ cat /etc/passwd
root:x:0:1:Super-User:/:/sbin/sh
daemon:x:1:1::/:
bin:x:2:2::/usr/bin:
sys:x:3:3::/:
adm:x:4:4:Admin:/var/adm:
lp:x:71:8:Line Printer Admin:/usr/spool/lp:
uucp:x:5:5:uucp Admin:/usr/lib/uucp:
nuucp:x:9:9:uucp Admin:/var/spool/uucppublic:/usr/lib/uucp/uucico
listen:x:37:4:Network Admin:/usr/net/nls:
nobody:x:60001:60001:Nobody:/:
noaccess:x:60002:60002:No Access User:/:
nobody4:x:65534:65534:SunOS 4.x Nobody:/:
oracle:*:101:67:DBA Account:/export/home/oracle:/bin/csh
webuser:*:102:102:Web User:/export/home/webuser:/bin/csh
abuzneid:x:103:100:Abdelshakour Abuzneid:/home/abuzneid:/sbin/csh
$
Logging in a UNIX system (continue.)
login: Skan
password:
$
/bin/sh
login:
UNIX
SYSTEM
KERNEL
/usr/lbin/ksh
/usr/data/bin
/dat_entry
login: Med
password:
$
login:
login: slim
password:
$
After Shell starts

When shell starts up, it displays a
command prompt:




$ in Bourne shell and Korn shell
% in C shell
Shell goes to sleep after every
command or program followed by
RETUN until the program has finished
This copied program is called a process
Login cycle
init
init
init
getty
init
sh
init
login
Login cycle (continue.)
Developed
by
Stephen
Bourne
Shell name
Utility
Bourne shell
sh
Korn shell
ksh
David Korn
C shell
csh
Bill Joy
Responsibilities of Shell






Program Execution
Variable and File Name Substitution
I/O Redirection
Pipeline Hookup
Environment Control
Interpreted Programming Language
Program Execution



Format: program-name arguments
The shell scans the command line and
determines the name of the program to
be executed and what argument to
pass to the program
Multiple occurrences of white spaces
characters are simple learned
Program Execution (continue.)

$ mv oldfile newfile
mv

arguments
oldfile
newfile
$ echo Smile, you are in Bridgeport City
Smile, you are in Bridgeport City
Smile,
$
you
echo
arguments
are
in
Bridgeport
City
Program Execution (continue.)


Shell has some built_in commands which
execute them directly without searching the
disk
cd, pwd and echo are built_in commands
Variables and File Name Substitution

assign values to variables

file name substitution on the command line
$ list=ls
$ ls
Carthage
Damas
$ $list
Carthage
Damas



*
?
[]
Variables and File Name Substitution
(continue.)
• Examples
$ ls
Documents
$
Memos mail personal
Variables and File Name Substitution
(continue.)
$ echo *
Documents Memos mail personal
$
arguments
echo
Documents
Memos
mail
personal
Variables and File Name Substitution
(continue.)
$ ls Documents mail
Documents:
a.doc
mail:
p1
$
p2
c.doc
p1
p11
Input/Output Redirection
<
<<
Input
Here
Document
Output
Output
>
>>
• Examples
$ wc -l list
2 list
$ wc -l < list
2
$
Input From a file
Read From Shell
Script
Direct to a File
Append to a File
Input/Output Redirection (continue.)
wc
wc
arguments
-l
users
arguments
-l
Input/Output Redirection (continue.)


In the first command line, two
arguments where passed to wc (word
count) utility: -l and users
In the second command line, one
argument is passed to wc utility: -l. This
gives the indication that the number of
lines appearing on standard input is to
count
Pipeline Hookup


Connects to commands
Pipe characters:



|
^
Connects the standard output from the
command preceding | to the standard
input of the one following the |
Pipeline Hookup (continue.)

Example:
$ who | wc -l

Counts the number of users login to the
system by connecting the standard
output of who to the standard output
for wc
Basic Unix commands









cat file
cat file1 file2 ...
cd directory1
cd /usr/bin
cd
clear
cp file1 file2
cp file1 file2 ... dir
ls
ls /usr/bin
lpr file1
lpr file1 file2 ...
more file
mkdir directory
mv file1 file2
mv file1 file2 ... dir
mv dir1 dir2
Concatenate or type out a file
Type out a number of files
Change current directory to directory1
Change current directory to /usr/bin
Change back to your home directory
Clear the current screen
Copy file1 to file2
Copy a number of files to a directory
List the files in the current directory
List the files in the /usr/bin directory
Print file1 out
Print a number of files out
Look at the content of a file with paging, use ‘q’ to get out
Create a directory
Move file1 to file2, like rename.
Move a number of files into a directory
Move or rename a directory

Basic Unix commands (continue)
• rm file
rm file1 file2 ..
rm -r directory
• rmdir directory
Remove a file
Remove a number of files
Remove a directory include the sub-directory
Remove a directory
Unix commands vs DoS

DOS Command
Unix Command
Descriptions
CD
CHKDSK
CLS
COPY
DEL
DIR
MD
MORE
PRINT
RD
RENAME
TYPE
cd
du
clear
cp
rm
ls
mkdir
more
lpr
rmdir
mv
cat
Change directory
Disk usage
Clear the current screen
Copying files
Removing files or directories
File listing of directories
Create a directory
Type out a file with paging
Print out a file
Remove a directory
Moving files around
Type out files
and Where?

man cp
Display on-line manual for the “cp” command
man -k keyword
Display manual help file related to the keyword
passwd
Change your login password
pwd
Display the path name of where you are
uptime
Tell you how long the machine has been up and running
users
Tell you who is logging in
who
Tell you who is logging-in in detail
w
Tell you who is logging in and doing what!
whoami
Show you the owner of this account
finger user
Find out the personal information of a user
finger name
Try to find the person’s info. by his/her name
finger email-address
Try to find the person’s info across the network
write user
Write a message on somebody’s screen
talk user
Talk to the person logging in the same system with you
talk email-address Talk to somebody logging in the network
date
Display today’s time and date

cal year












Display the calendar of the specified
year (e.g. 1997)
References




http://info.ee.surrey.ac.uk/Teaching/Unix/
UNIX SHELLS BY EXAMPLE BY ELLIE
QUIGLEY
UNIX FOR PROGRAMMERS AND USERS BY G.
GLASS AND K ABLES
UNIX SHELL PROGRAMMING BY S. KOCHAN
AND P. WOOD